This invention relates to improvements in prime movers, such as tractors and like vehicles, particularly those using movable control members in the power transmission mechanisms thereof. More specifically, this invention is in the nature of a control device or interlock for preventing the engine of a vehicle, such as a tractor, from being started when the driving wheels or other power operated mechanisms of the vehicle are operatively coupled to the vehicle engine. The invention is particularly adapted to vehicles such as tractors having hydrostatic drive assemblies including one or more pumps driven by an internal combustion engine, and cooperating fluid motors connected to the vehicle drive wheels or other power driven apparatus. In many cases, the engine driven pumps are of the well known wobble plate controlled variety and operate between neutral, stationary, and forward and reverse drive dispositions.
The vehicle operator, in starting the tractor engine, does not always notice whether or not the drive mechanisms are in a neutral state. If the hydrostatic system is in a drive condition, the vehicle starts to move immediately upon starting of the engine. If the operator is not prepared for sudden unexpected movement, accidents may occur. An important object of this invention is, therefore, the provision of means for preventing a vehicle engine from being started unless the power transmission mechanism of the vehicle is in a neutral nonoperative state.